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Pension and Postretirement Plans (Narrative) (Details) - Defined Benefit Pension Plan [Member]
$ in Thousands
3 Months Ended 12 Months Ended
Mar. 31, 2023
USD ($)
investment
company
Mar. 31, 2022
USD ($)
Dec. 31, 2022
USD ($)
investment
Defined Benefit Plan Disclosure [Line Items]      
Special separation benefit expense $ 4,129 $ 0  
Percent of plan assets managed internally by the company 41.00%    
Percent of plan assets managed by investment companies 59.00%    
Number of investment companies actively managing plan assets | company 2    
Percentage of total plan assets 100.00%   100.00%
Berkshire Hathaway Common Stock [Member] | Investment Manager 2 [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined benefit plan, target allocation maximum percentage of assets, singular equity security, without prior approval by plan administrator 20.00%    
Alphabet and Berkshire Hathaway Common Stock [Member] | Investment Manager 1 [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined benefit plan, target allocation maximum percentage of assets, singular equity security, without prior approval by plan administrator 15.00%    
Foreign Investments [Member] | Maximum [Member] | Investment Manager 1 [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined benefit plan, target allocation percentage of assets 30.00%    
Foreign Investments [Member] | Maximum [Member] | Investment Manager 2 [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined benefit plan, target allocation percentage of assets 15.00%    
Fixed income securities [Member] | Minimum [Member] | Investment Manager 2 [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined benefit plan, target allocation percentage of assets 10.00%    
Private investment fund [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Percentage of total plan assets 17.00%   16.00%
Single Equity Concentration [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined benefit plan, target allocation maximum percentage of assets, singular equity security, without prior approval by plan administrator 10.00%   10.00%
Value of investments $ 876,600   $ 842,600
Percentage of total plan assets 33.00%   33.00%
Single Equity Concentration [Member] | Equity Securities [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Number of investments the company's pension plan held which individually exceed 10% of total plan assets | investment 1   1
Single Equity Concentration [Member] | Private investment fund [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Number of investments the company's pension plan held which individually exceed 10% of total plan assets | investment 1   1
Concentration In Single Entity, Type Of Industry, Foreign Country Or Individual Fund [Member] | Defined Benefit Plan Assets Total [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Minimum percentage of plan assets considered as significant concentrations in pension plans 10.00%    
Leaf Group and Code3 [Member] | Separation Incentive Program [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Special separation benefit expense $ 4,100